Twin clutch rear axle torque distributing system

ABSTRACT

A clutch assembly for disposition in a motor vehicle drive line includes an internal reaction force circuit. The clutch assembly includes a multiple disc friction clutch disposed adjacent an operator assembly which selectively applies force to the friction clutch to selectively transfer torque therethrough. The clutch components are disposed between a flange and a stop on an elongate member which functions as a reaction force member to self-contain the reaction force from the clutch operator. The clutch finds particular application in motor vehicle drive line components such as a rear (secondary) axle wherein it is disposed in pairs to independently control torque supplied to each axle and in applications where it is advantageous to contain or ground the reaction force generated by and associated with the clutch operator compactly within the clutch structure rather than its housing.

CROSS REFERENCE TO CO-PENDING APPLICATION

This application is a divisional application of Ser. No. 09/272,460,filed Mar. 19, 1999 now U.S. Pat. No. 6,098,770 granted Aug. 8, 2000.

BACKGROUND OF THE INVENTION

The invention relates generally to multiple friction plate clutches formotor vehicle drive line components and more specifically to frictionplate clutches having an internal reaction force circuit for use inpairs with a front or rear axle.

Vehicle drive line and control systems having both electric andhydraulic modulating clutches have found broad application in adaptivevehicle drive systems. Such systems generally monitor the speeds of thefront and rear drive shaft or compute such speeds by averagingindividual readings of the two front and two rear wheels and, upondetermining a speed difference between the drive shaft speeds or averagespeeds of the wheels, energize the modulating clutch according to apredetermined program to drive the speed difference and thus wheel sliptoward zero. Such systems may also monitor and adjust modulating clutchactivity in response to throttle position, steering angle and othervariables.

Typically, such modulating clutches are physically disposed in atransfer case, adjacent and driven by the output of the vehicletransmission, and operably disposed between the primary and secondarydrive lines. Such systems are disposed in co-owned U.S. Pat. No.5,407,024 granted Apr. 18, 1995 and U.S. Pat. No. 5,485,894 granted Jan.23, 1996.

An alternate approach to vehicle skid control comprehends association ofan individually operable clutch with each axle of a secondary, that is,part-time drive line. Selective, modulating activation of one or both ofthe clutches directs drive torque to one or both secondary drive wheelsto adjust or correct vehicle yaw. An early system utilizing hydraulicclutches is disclosed in U.S. Pat. No. 4,681,180. Here, a control unithaving steering angle, vehicle speed and engine torque inputs and adjusttorque distribution between only the two rear wheels.

U.S. Pat. Nos. 5,195,901 and 5,119,900 both teach a vehicle having twoindependently operable rear axle clutches in a drive line which providesprimary drive torque to the front wheels and selectively andindependently provides torque to the rear wheels.

In U.S. Pat. No. 5,353,889, a rear axle includes a pair of hydraulicallyoperated independent clutches controlled by associated hydraulicpressure clutches and pumps.

In U.S. Pat. No. 5,383,378, a twin clutch axle disposed at the front ofa vehicle provide drive torque to the front (secondary) drive wheel inresponse to steering angle. U.S. Pat. No. 5,540,119 teaches adifferential drive assembly for transferring rotational power withoutthe use of conventional differential gearing. The device utilizes pairsof clutches and cam mechanisms which actuate said clutches in response apredetermined relative rotation.

While many problems have been addressed and new operational schemesachieved by the devices found in the prior art, it is apparent thatcertain problems have not been addressed. For example, it should beappreciated that, according to Newton's third law of motion, the director action force generated by a clutch operator to compress an adjacentclutch pack creates an equal and opposite reaction force which istransmitted through whatever structural components of the clutchassembly constitute the reaction force path or circuit.

Typically, such reaction force path will be through or contained in anouter housing in devices where the clutch pack is disposed adjacent theclutch operator and both are contained within the housing. Such aconfiguration can apply significant reaction force, not only to thehousing, but also to whatever fasteners are utilized to secure thehousing components together. Such a configuration can bedisadvantageous, causing either fastener or housing failure ornecessitating heavy and therefore costly housing and fastenerconfigurations. Accurately controlled modulation of the clutches mayalso be compromised due to flexure or distortion of the housing or othercomponents in the reaction force path. Accordingly, the operation ofdevices containing such clutches may be compromised. The presentinvention addresses such matters.

SUMMARY OF THE INVENTION

A clutch assembly for disposition in a motor vehicle drive line includesan internal reaction force circuit. The clutch assembly includes amultiple plate or disc friction clutch disposed adjacent an operatorassembly which selectively applies compressive force to the frictionclutch to selectively transfer torque therethrough. The clutchcomponents are disposed on an elongate member. The elongate memberincludes a preferably integrally formed circular plate or flange whichfunctions as a first stop against which one side of the clutch packabuts. A circular collar which may, in fact, be an anti-friction bearingis retained on the elongate member by a pair of snap rings. The circularcollar or anti-friction bearing functions as a second stop against whichone side of the operator assembly abuts. The elongate member thusfunctions as a reaction force member and self-contains the reactionforce generated by the clutch operation. The clutch operator may be aball ramp assembly which is actuated by an electromagnetic coil.Alternatively, the operator may include an electric motor and camassembly which generates compressive force. Direct acting hydraulic orair driven piston and cylinder operators or pilot and main clutcheswhich are electrically, pneumatically or hydraulically operated are alsouseful with and within the scope of the present invention.

The clutch finds application in motor vehicle drive line components suchas a rear (secondary) axles in which it is disposed in pairs toindependently control torque supplied to each axle and in otherapplications where it is advantageous to contain or ground the reactionforce generated by and associated with the clutch operator within theclutch structure rather than its housing.

It is thus an object of the present invention to provide a multiplefriction plate clutch having an internal reaction force path.

It is a still further object of the present invention to provide amultiple friction plate clutch and operator which are juxtaposed upon anelongate member which functions as the reaction force return path.

It is a still further object of the present invention to provide amultiple plate friction clutch assembly having an internal reactionforce path for use in motor vehicle drive lines.

It is a still further object of the present invention to provide amultiple plate friction clutch assembly having an internal reactionforce circuit for use in pairs in a rear (secondary) axle independentlycontrolling torque delivery to associated wheels.

It is a still further object of the present invention to provide amultiple friction plate clutch and operator assembly are juxtaposed andassembled upon a common member which functions as a reaction forcecontaining member.

Further objects and advantages of the present invention will becomeapparent by reference to the following description of the preferredembodiment and appended drawings wherein like numbers refer to the samecomponent, element or feature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a vehicle drive system for a four-wheelvehicle incorporating the twin clutch axle of the present invention;

FIG. 2 is a full, sectional view of a twin clutch axle incorporatingclutches having internal reaction force circuits according to thepresent invention and,

FIG. 3 is an enlarged, sectional view of a clutch having an internalreaction force circuit according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, an adaptive four-wheel vehicle drive trainincorporating the present invention is diagrammatically illustrated anddesignated by the reference number 10. The four-wheel vehicle drivetrain 10 includes a prime mover 12 which is coupled to and directlydrives a transaxle 14. The output of the transaxle 14 drives a beveledor spiral beveled gear set 16 which provides motive power to a primaryor front drive line 20 comprising a front or primary propshaft 22, afront or primary differential 24, a pair of live front axles 26 and arespective pair of front or primary tire and wheel assemblies 28. Itshould be appreciated that the front or primary differential 24 isconventional.

The beveled or spiral beveled gear set 16 also provides motive power toa secondary or rear drive line 30 comprising a secondary propshaft 32having appropriate universal joints 341 a rear or secondary differentialassembly 36, a pair of live secondary or rear axles 38 and a respectivepair of secondary or rear tire and wheel assemblies 40. As utilizedherein with regard to the secondary differential assembly 36, the terms“differential” and “axle” are used interchangeably to identify a devicefor receiving drive line torque, distributing it to two transverselydisposed wheels and accommodating rotational speed differences resultingfrom, inter alia, vehicle cornering. As such, the terms are intended toinclude devices such as the present invention which provide thesefunctions but which do not include a conventional epicyclic gear train.

The foregoing description relates to a vehicle wherein the primary driveline 20 is disposed at the front of the vehicle and, correspondingly,the secondary drive line 30 is disposed at the rear of the vehicle, sucha vehicle commonly being referred to as a front wheel drive vehicle. Thedesignations “primary” and “secondary” utilized herein refer to drivelines providing drive torque at all times and drive lines providingsupplemental or intermittent torque, respectively. These designations(primary and secondary) are utilized herein rather than front and rearin as much as the invention herein disclosed and claimed may be readilyutilized with vehicles wherein the primary drive line 20 is disposed atthe rear of the vehicle and the secondary drive line 30 and componentswithin the secondary differential assembly 36 are disposed at the frontof the vehicle.

Thus, the illustration in FIG. 1, wherein the primary drive line 20 isdisposed at the front of the vehicle should be understood to beillustrative rather than limiting and that the components and thegeneral arrangement of components illustrated is equally suitable andusable with a primary rear wheel drive vehicle. In such a vehicle, theprimary differential 24 would replace the secondary differentialassembly 36 at the rear of the vehicle and the secondary differentialassembly 36 would be moved to the front of the vehicle to replace theprimary differential 24.

Associated with the vehicle drive train 10 is a microprocessor 50 whichreceives signals from a plurality of sensors and provides two control,i.e., actuation signals to the secondary differential assembly 36.Specifically, a first sensor such as a variable reluctance or Halleffect sensor 52 senses the rotational speed of the left primary (front)tire and wheel assembly 28 and provides an appropriate signal to themicroprocessor 50. Similarly, a second variable reluctance or Halleffect sensor 54 senses the rotational speed of the left primary (front)tire and wheel assembly 28 and provides a signal to the microprocessor50. A third variable reluctance or Hall effect sensor 56 senses therotational speed of the right secondary (rear) tire and wheel assembly40 and provides a signal to the microprocessor 50. Finally, a fourthvariable reluctance or Hall effect sensor 58 associated with the leftsecondary (rear) tire and wheel assembly 40 senses its speed andprovides a signal to the microprocessor 50. It should be understood thatthe speed sensors 52, 54, 56 and 58 may be independent, i.e., dedicated,sensors or may be those sensors mounted in the vehicle for anti-lockbrake systems (ABS) or other speed sensing and control equipment. It isalso to be understood that an appropriate and conventional counting ortone wheel is associated with each of the speed sensors 52, 54, 56 and58 although they are not illustrated in FIG. 1.

In order to provide optimum skid or yaw control, the microprocessor 50also requires information regarding the output speed of the transaxle14. Accordingly, a variable reluctance or Hall effect sensor 62 which isassociated with a tone wheel 64 on the front or primary prop shaft 22may be utilized. In the alternative, a variable reluctance or Halleffect sensor 66 associated with the secondary differential assembly 36and positioned adjacent a tone wheel 68 on an input shaft 70 of thesecondary differential assembly 36 may also be utilized. Themicroprocessor 50 includes software which receives and conditions thesignals from the sensors 52, 54, 56 and 58 as well as either the sensor62 or the sensor 66, determines corrective action to improve thestability of the vehicle, maintain control of the vehicle and/or correctand compensate for a skid or other anomalous yaw condition of thevehicle and provides two independent output signals to the secondarydifferential assembly 36.

Referring now to FIG. 2, the input shaft 70 of the secondarydifferential assembly 36 may include a flange 72 or similar componentwhich is secured to the input shaft 70 by a nut 74 or similar threadedfastener. The flange 72 forms a portion of a connection, such as auniversal joint 34 (illustrated in FIG. 1), to the secondary propshaft32. The input shaft 70 is received within a center housing 76 and issurrounded by a suitable oil seal 78 which provides a fluid imperviousseal between the housing 76 and an associated portion of the flange 72or the input shaft 70. The input shaft 70 is preferably rotatablysupported by a pair of anti-friction bearings such as the tapered rollerbearing assemblies 80. The input shaft 70 terminates in a hypoid orbeveled gear 82 having gear teeth 84 which mate with complementarilyconfigured gear teeth 86 on a ring gear 88 secured to a flange 92 on acentrally disposed tubular drive member 94 by suitable fasteners 96. Thetubular drive member 94 is rotatably supported at each end by anantifriction bearing such as the ball bearing assemblies 102. Thetubular drive member 94 defines a hollow interior 104 into which a pairof scavengers or scoops 106 collect and deliver cooling and lubricatingfluid from the interior of the center housing 76. The tubular drivemember 94 also includes sets of external or male splines or gear teeth108 adjacent each end.

Turning now to FIGS. 2 and 3, the secondary differential assembly 36includes a pair of left and right outer bell housings 114A and 114Bwhich mate with the center housing 76 along left and right parting lines116A and 116B and are attached to the center housing 74 by threadedfasteners 118. The housings 114A and 114B are mirror-image, i.e., leftand right, components which each receive and house a respective one of apair of modulating clutch assemblies 120A and 120B. But for the opposed,mirror-image arrangement of the two modulating clutch assemblies 120Aand 120B, the components of the two clutch assemblies 120A and 120Bdescribed below are identical and thus only the modulating clutchassembly 120B disposed on the right of FIG. 2 and in FIG. 3 will befully described, it being understood that the left modulating clutchassembly 120A is in all significant respects identical to the rightmodulating clutch assembly 120B.

Each of the modulating clutch assemblies 120A and 120B is driven by themale or external splines or gear teeth 108 of the tubular drive member94 which engage complementarily configured female or internal splines orgear teeth 122 on a bell housing 124. The bell housing includes aplurality of female or internal splines 126 on its circumferential innersurface 128. The internal splines 126 are engaged by and rotationallydrive complementarily configured male or external splines 132 disposedon a first plurality of larger diameter clutch plates or discs 134. Thefirst plurality of clutch plates or discs 134 includes suitable frictionmaterial and surfaces and are interleaved with a second plurality ofsmaller diameter clutch plates or discs 136.

The second plurality of smaller clutch discs 136 also includes suitablefriction material and surfaces and has female splines 138 which engageand rotationally drive complementarily configured male or externalsplines 140 disposed upon an annulus or collar 142. The collar 142, inturn, includes female or internal splines or gear teeth 146 which matewith complementarily configured male or external splines or gear teeth148 disposed on the output shaft 150B. The output shaft 150B includes apreferably integrally formed radially extending flange 154 having a flatannular pressure surface 156 against which the friction material of theinterleaved pluralities of clutch discs 134 and 136 abuts and aligns.Alternatively, of course, the flange 154 may be a separate componentwhich is secured to the output shaft 150B by any suitable means such aswelding or axially restrained thereon by a suitable shoulder or otherpositive stop.

On the opposite side of the radial flange 154 is a friction reducingflat washer 158 which axially spaces it from the tubular drive member 94and the bell housing 124. Adjacent the flat washer 158 and disposedbetween a counterbore in the drive tube 94 and a reduced diameterportion 162 of the output shaft 150B is a friction reducing bushing orjournal bearing 164.

The output shaft 150B also defines an axial bore 166 which communicateswith at least one radial passageway 168 through which cooling andlubricating fluid collected by the scavengers or scoops 106 (illustratedin FIG. 2) may flow to the disc pack clutch assembly 120B.

The disc pack clutch assembly 120B also includes a circular apply plate172 which includes female or internal splines or gear teeth 174 whichmate with the male splines 140 on the collar 142. The apply plate 172thus rotates with the second plurality of smaller diameter clutch plates136 and may move axially relative thereto. The apply plate 172 ispreferably fabricated of a non-magnetic metal such as stainless steel sothat it does not participate in nor interfere with the magnetic circuit(flux path) of the modulating clutch assembly 120B. The apply plate 172includes a shoulder 176 which positions and receives a flat washer 178.The flat washer 178 reduces friction between the apply plate 172 and acircular armature 182. The circular armature 182 includes a plurality ofdiscontinuous, arcuate, banana slots 184 and a plurality of male splines186 about its periphery which are complementary to and engage theplurality of female splines 126 on the interior of the bell housing 124.Thus, the circular armature 182 rotates with the bell housing 124 andthe first plurality of clutch plates 134.

The circular armature 182 is disposed adjacent a U-shaped circular rotor192. The rotor 192, which is preferably fabricated of soft iron,includes a pair of spaced apart pluralities of discontinuous, arcuate,banana slots 194 which cooperate with the banana slots 184 in thecircular armature 182 to create a sinuous magnetic flux path whichimproves operation of the disc pack clutch assembly 120B and increasesits torque throughput.

The rotor 192 generally surrounds a stationary housing 198 whichcontains an electromagnetic coil 200. The stationary housing 198 and theelectromagnetic coil 200 are secured to the outer housing 114B by aplurality of threaded studs and fasteners 202, two of which areillustrated in FIG. 2. Electrical energy is selectively provided to theelectromagnetic coil 200 through a conductor 204B, also illustrated inFIG. 2. Coupled to the rotor 192 by any suitable means such asweldments, interengaging splines or an interference fit and disposedconcentrically about the output shaft 150B is a first circular member210. A low friction collar 212 made of, for example, nylon is interposedthe first circular member 210 and the output shaft 150B and thus thefirst circular member 202 and the rotor 192 are free to rotate aboutboth the output shaft 150B and the housing 198 of the electromagneticcoil 200. The low friction collar 212 reduces friction between the firstcircular member 210 and the output shaft 150B when the disc pack clutchassembly 120B is deactivated, thereby reduced drag wear and heatgeneration.

The first circular member 210 includes a plurality of curved ramps orrecesses 214 arranged in a circular pattern about the axis of the outputshaft 150B. The ramps or recesses 214 represent oblique sections of ahelical torus. Disposed within each of the recesses 214 is one of a likeplurality of load transferring balls 216 or similar load transferringmembers which rolls along the ramps defined by the oblique surfaces ofthe recesses 214. A second circular member 218 is disposed in opposedrelationship with the first circular member 210 and includes a likeplurality of complementarily sized and arranged ramped recesses 222. Theload transferring balls 216 are thus received and trapped within thepairs of opposing recesses 214 and 222, the ends of the recesses beingcurved and much steeper in slope than the interior regions of therecesses 214 and 222 such that the load transferring balls 216 areretained therein. A plurality of wave washers or Belleville springs 224are disposed between the second circular member 218 and the collar 142and bias the second circular member 218 toward the first circular member210.

It will be appreciated that the plurality of ramped recesses 214 and 222and the load transferring balls 216 may be replaced with other analogousmechanical elements which cause axial displacement of the circularmembers 210 and 218 in response to relative rotation therebetween. Forexample, tapered rollers disposed in complementarily configured conicalhelices may be utilized.

An important design consideration of the recesses 214 and 222, the loadtransferring balls 216 and the Belleville springs 224 is that thegeometry of their design and the overall clearances in the clutchassemblies 120A and 120B ensure that they are not self-engaging. Themodulated clutch assemblies 120A and 120B must not self-engage butrather must be capable of modulated clamping of the clutch plates 134and 136 and torque transfer in direct, proportional response to theelectrical input to the electromagnetic coil 200. Additional details ofthis mechanism may be found in U.S. Pat. No. 5,492,194 which is herebyincorporated by reference.

The second circular member 218 includes a plurality of female splines orgear teeth 228 which are complementary to and engage the male splines orgear teeth 148 on the output shaft 150B. A flat washer 230 transfersaxial force from the second circular member 218 to the apply plate 172.The axial position of the first circular member 210 is established by athrust bearing assembly 232. Adjacent the thrust bearing assembly 232 isan anti-friction bearing such as a ball bearing assembly 234 whichrotatably supports and axially locates the output shaft 150B within thehousing 114B. The ball bearing assembly 234 is axially located andrestrained by a pair of snap rings 236 which are received withincomplementarily configured circumferential slots or grooves 238. Theoutput shaft 150B also includes a set of external or male splines orgear teeth 240 which are adapted and intended to mate withcomplementarily configured female splines, gear teeth or an outputflange, shaft or axle (all not illustrated). An oil seal 242 provides anappropriate fluid tight seal between the housing 114B and the outputshaft 150B.

A brief description of the operation of the disc pack clutch assembly120B of the rear differential assembly 36 highlights the improvementsand features thereof. When the electromagnetic coil 200 is notenergized, the output shaft 150B freewheels relative to the tubularinput member 94 which functions as the input drive member. As currentflow to the electromagnetic coil 200 commences and increases, drag iscreated which attempts to slow rotation of the rotor 192, causingrelative rotation between the first and second circular members 210 and218. As this occurs, the load transferring balls 216 ride up therecesses 214 and 222, separate the first and second circular members 210and 218 and drive the second circular member 218 toward the apply plate172. Translation of the apply plate 172 compresses the pluralities ofclutch discs 134 and 136 and transfers drive torque from the tubulardrive member 94 and the bell housing 124 to the collar 142 and the rightoutput shaft 150B. Activation of the left modulating clutch assembly120A results in corresponding torque transfer to the left output shaft150A (illustrated in FIG. 2).

It should be noted that the compressive force generated by the first andsecond circular members 210 and 218 passes through the washer 230,through the apply plate 172, the pluralities of clutch plates 134 and136, through the radial flange 154 and into the output shaft 150B.Reaction force is thus carried axially along the length of the outputshaft 150B, through the snap rings 236, the ball bearing assembly 234and the thrust bearing 232 and thence back to the first circular member210. The radial flange 154 on the output shaft 150B and the snap rings236 thus act as fixed stops which confine the components of the discpack clutch assembly 120B and direct the reaction force from itsoperation into and along the output shaft 150B. It will thus beappreciated that the reaction force generated by operation of the discpack clutch assembly 120B is effectively fully contained within theoutput shaft 150B and does not pass through the outer housing 114B, thecenter housing 76 or other components. Such direct containment of theclutch operator reaction force reduces forces and flexure of thehousings 76, 114A and 114B and improves the modulating control andservice life of the rear differential assembly 36 and its components.

It should also be noted that while the above-described preferredembodiment of a clutch having an internal reaction force circuitutilizes an electromagnetic operator, a piston and cylinder arrangementutilizing either hydraulic fluid or a gas under pressure such as air areall readily adaptable to actuate the clutch pack and realize thefeatures and benefits of the internal reaction force path or circuit ofthe present invention. Thus, such various clutch actuator configurationsare deemed to be well within the scope of the present invention.

Finally, it should be understood that while the output shaft 150B hasbeen described above as the reaction force containing member, thedirection of torque flow through the multiple disc pack clutch assembly120B may readily be reversed or the clutch assembly 120B may bereconfigured such that the shaft 150B is the input shaft. In eithercase, the shaft 150B functions as the reaction force containing member.

The foregoing disclosure is the best mode devised by the inventor forpracticing this invention. It is apparent, however, that apparatusincorporating modifications and variations will be obvious to oneskilled in the art of drive line clutch components. In as much as theforegoing disclosure is intended to enable one skilled in the pertinentart to practice the present invention, it should not be construed to belimited thereby but should be construed to include such aforementionedobvious variations and be limited only by the spirit and scope of thefollowing claims.

I claim:
 1. A torque distributing system for use in a motor vehiclecomprising, in combination, an input, a pair of outputs, adapted todrive a respective pair of tire and wheel assemblies, a modulatingclutch disposed between said input and each of said pair of outputs,said modulating clutches having a first plurality of clutch discsdisposed for rotation with said input, a second plurality of clutchdiscs interleaved with said input, first plurality of clutch discs anddisposed for rotation with a respective one of said pair of outputs andan operator for frictionally engaging said first and said secondpluralities of clutch discs, a pair of elongate members each having aflange defining an annular surface adapted to engage one of said clutchdiscs and a stop spaced from said flange, said modulating clutchesdisposed in a respective one of said pair of elongated members betweensaid flange and said stop, a pair of sensing assemblies for sensingrespective speeds of said pair of outputs, and a microprocessor operablyassociated with said pair of sensing assemblies and having a pair ofelectrical outputs driving a respective one of said operators.
 2. Thetorque distributing system of claim 1 wherein said flange is integrallyformed on said elongate members.
 3. The torque distributing system ofclaim 1 wherein said operator includes a stationary electromagneticcoil, an armature, a rotor and a ball ramp operator.
 4. The torquedistributing system of claim 3 wherein said ball ramp operator includesa pair of opposed circular members defining complementarily configuredopposed ramped recesses and rolling members disposed in said recesses.5. The torque distributing system of claim 1 wherein said input is aportion of a bevel gear set on a first axis driven by a gear on a secondaxis normal to said first axis.
 6. The torque distributing system ofclaim 5 further including a member driving said gear and a third sensingassembly for sensing the speed of said member.
 7. The torquedistributing system of claim 1 wherein said pair of outputs are saidpair of elongate members.
 8. A torque distributing system for use in amotor vehicle comprising, in combination, an input, an input member; apair of outputs, driving a respective pair of axles, a pair ofmodulating clutches disposed between said input member and a respectiveone of said pair of outputs, said pair of modulating clutches having afirst plurality of clutch discs disposed for rotation with said inputmember, a second plurality of clutch discs interleaved with said firstplurality of clutch discs and disposed for rotation with a respectiveone of said pair of outputs and an operator for engaging said first andsaid second pluralities of clutch discs, said pair of outputs eachhaving a flange defining an annular surface engaging one of said clutchdiscs and a stop spaced from said flange, one of said pair of modulatingclutches disposed on a respective one of said pair of outputs betweensaid flange and said stop, and a pair of speed sensing assembliesoperably associated with a respective one of each of said pair of axles.9. The torque distributing system of claim 8 wherein said operatorincludes an electromagnetic coil, an armature, a rotor and a ball rampoperator.
 10. The torque distributing system of claim 9 wherein saidball ramp operator includes a pair of opposed circular members definingcomplementarily configured opposed ramped recesses and rolling membersdisposed in said recesses.
 11. The torque distributing system of claim 8wherein said input member is a bevel gear on a first axis driven by agear on a second axis normal to said first axis.
 12. The torquedistributing system of claim 11 further including a member driving saidgear and a third speed sensing assembly for sensing the speed of saidmember.
 13. The torque distributing system of claim 8 further includinga microprocessor operably associated with said pair of speed sensingassemblies and having a pair of electrical outputs driving a respectiveone of said pair of operators.
 14. The torque distributing system ofclaim 13 wherein said pair of speed sensing assemblies provide signalsto an ABS system in the vehicle.
 15. A torque distributing system foruse in a motor vehicle comprising, in combination, an input, a firstgear disposed for rotation on a first axis, an second gear driven bysaid first gear and disposed for rotation on a second axis normal tosaid first axis, a pair of output members, each of said pair of outputmembers driving a respective pair of axles, a pair of modulatingclutches operably disposed between said second gear and respective oneof said pair of output members, each of said pair of modulating clutcheshaving a first plurality of clutch members disposed for rotation withsaid input, a second plurality of said clutch members interleaved withsaid first plurality of said clutch members and disposed for rotationwith a respective one of said pair of outputs and an operator forcompressing said first and said second pluralities of clutch members,said pair of output members each having a radial flange having anannular surface adapted to engage one of said clutch discs and a stopspaced from said flange, one of said pair of modulating clutchesdisposed on a respective one of said pair of output members between saidflange and said stop, a pair of sensor assemblies for sensing respectivespeeds of said pair of axles, and a microprocessor operably associatedwith said pair of sensor assemblies and having a pair of outputs drivinga respective one of said operators.
 16. The torque distributing systemof claim 15 wherein said operator includes an electromagnetic coil, anarmature, a rotor and a ball ramp operator.
 17. The torque distributingsystem of claim 16 wherein said ball ramp operator includes a pair ofopposed circular members defining complementarily configured opposedrecesses and rolling members disposed in said recesses.
 18. The torquedistributing system of claim 15 wherein said flange is integrally formedon said elongate members.
 19. The torque distributing system of claim 15further including a member driving said drive gear and a third sensorassembly for sensing the speed of said member.
 20. The torquedistributing system of claim 15 wherein said pair of sensor assembliesalso form a portion on the vehicle anti-lock brake system.